Using a rear wheel suspension device of an automobile to perform inverse phase toe angle control, where the rear wheels are given toe angle of the opposite phase as the steering angle yields advantages such as improved steering properties during low-speed turning, and improved drivability due to an improved vehicle attitude angle. Also, a configuration which enables the camber angle of the rear wheels to be changed is advantageous in that the running resistance is reduced as rolling resistance is reduced due to reduction in ground contact area.
Related art regarding such rear-wheel camber angle and toe angle includes using a strut-type rear wheel suspension device originally configured to include struts made up of dampers and springs, and lower arms, to adjust the camber angle of the rear wheels by driving the knuckles by pushing and pulling with motors so as to turn the knuckles on the camber shafts. The lower ends of the knuckles are also linked to the lower arms by ball joints, thereby enabling the toe angle of the rear wheels to be adjusted (see Japanese Unexamined Patent Application Publication No. 2011-116164).
However, the above related art uses motors which serve as actuators to adjust only the camber angle of the rear wheels, thus separate actuators have to be provided if the toe angle of the rear wheels is also to be adjusted. This configuration would be problematic in that unstrung weight increases, and so forth.
Also, inverse phase toe angle control, where the rear wheels are given toe angle of the opposite phase to the steering angle of the front wheels, yields advantages such as improved steering properties during low-speed turning and improved drivability. However, applying inverse phase toe angle control based on such low-speed turning to high-speed turning as well causes a problem of poorer stability due to the inverse phase toe angle. Accordingly, it would be difficult to realize desirable performance for both low-speed turning and high-speed turning.
One solution would be controlling the rear wheel toe angle in accordance with the vehicle speed. On the other hand, applying toe angles of opposite directions and of different absolute values to the left and right rear wheels results in the toe angle substantially changing in accordance with the lateral acceleration placed on the vehicle when turning, thus a state is realized where a suitable toe angle according to vehicle speed is given, even without controlling the toe angle in accordance with the vehicle speed. Therefore, steering properties during low-speed turning and drivability can be improved while preventing deterioration in stability during high-speed turning.